Piperidine compounds a tetrahydrofuran ring for use as stabilisers for organic material

ABSTRACT

The present invention relates to novel tetramethylpiperidine compounds of the general formula (I)   f the formula (IIa) or (IIb)    &lt;IMAGE&gt;  (IIa)   &lt;IMAGE&gt;  (IIb)  in which R1 and R2 are e.g. hydrogen or methyl. The said compounds are effective stabilizers for organic materials, in particular synthetic polymers, against the action of light, heat and oxidation.

This application is a continuation of application Ser. No 08/008,058, filed Jan. 22, 1993, now abandoned; which is a continuation of Ser. No. 07/891,531, filed Jun. 1, 1992, now abandoned.

The present invention relates to novel piperidine compounds, to the use thereof as light stabilisers, heat stabilisers and oxidation stabilisers for organic materials, in particular synthetic polymers, and to organic materials thus stabilised.

Numerous patents on the preparation and use, as light stabilisers for synthetic polymers, of derivatives of 2,2,6,6-tetramethylpiperidine have been published, in particular U.S. Pat. Nos. 3,640,928, 3,684,765, 3,840,494, 3,904,581, 4,021,432, 4,136,081 and 4,798,836 and DE 3,522,678.

The present invention relates to novel piperidine compounds of the general formula (I) ##STR3## in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) ##STR4## in which R₁ is hydrogen, C₁ -C₈ alkyl, O, OH, NO, CH₂ CN, C₁ -C₁₈ alkoxy, C₅ -C₁₂ cycloalkoxy, C₃ -C₆ alkenyl, C₇ -C₉ phenylalkyl which is unsubstituted or mono-, di- or tri-substituted on the phenyl by C₁ -C₄ alkyl; or C₁ -C₈ acyl and R₂ is hydrogen, C₁ -C₁₈ alkyl, C₃ -C₆ alkenyl, C₂ -C₄ alkyl substituted in the 2-, 3- or 4-position by C₁ -C₈ alkoxy, by di(C₁ -C₄ alkyl)amino or by a 5- to 7-membered nitrogen-containing heterocyclic group with the free valency on the nitrogen atom; C₅ -C₁₂ cycloalkyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl; C₇ -C₉ phenylalkyl which is unsubstituted or mono-, di- or tri-substituted on the phenyl by C₁ -C₄ alkyl; tetrahydrofurfuryl or a group of the formula (III) ##STR5## with R₁ being as defined above, or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR6## with R being a group of the formula (III).

Examples of alkyl having not more than 18 carbon atoms are methyl, ethyl, propyl, isopropyl, butyl, 2-butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl or octadecyl.

Examples of C₂ -C₄ alkyl substituted by C₁ -C₈ alkoxy, preferably C₁ -C₄ alkoxy, in particular methoxy or ethoxy, are 2-methoxyethyl, 2-ethoxyethyl, 3-methoxypropyl, 3-ethoxypropyl, 3-butoxypropyl, 3-octoxypropyl or 4-methoxybutyl.

Examples of C₂ -C₄ alkyl substituted by di(C₁ -C₄ alkyl)-amino, preferably by dimethylamino or diethylamino, are 2-dimethylaminoethyl, 2-diethylaminoethyl, 3-dimethylaminopropyl, 3-diethylaminopropyl, 3-dibutylaminopropyl or 4-diethylaminobutyl.

Examples of C₂ -C₄ alkyl substituted by a 5- to 7-membered nitrogen-containing heterocyclic group are the groups of the formula ##STR7## in which A is a direct bond, --O--,--CH₂ -- or --CH₂ CH₂ --. ##STR8## is preferred.

Examples of C₁ -C₁₈ alkoxy are methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentoxy, isopentoxy, hexoxy, heptoxy, octoxy, decyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy or octadecyloxy. C₆ -C₁₂ alkoxy is preferred.

Examples of C₅ -C₁₂ cycloalkyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl are cyclopentyl, methylcyclopentyl, dimethylcyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, trimethylcyclohexyl, t-butylcyclohexyl, cyclooctyl, cyclodecyl or cyclododecyl. Unsubstituted or C₁ -C₄ alkyl-substituted cyclohexyl is preferred.

Examples of C₅ -C₁₂ cycloalkoxy are cyclopentoxy, cyclohexoxy, cycloheptoxy, cyclooctoxy, cyclodecyloxy and cyclododecyloxy. Cyclopentoxy and cyclohexoxy are preferred.

Examples of C₃ -C₆ alkenyl are allyl, 2-methylallyl, 2-butenyl or 2-hexenyl. Allyl is preferred. The carbon atom in the 1-position is preferably saturated.

Examples of C₇ -C₉ phenylalkyl which is unsubstituted or mono-, di- or tri-substituted on the phenyl by C₁ -C₄ alkyl are benzyl, methylbenzyl, dimethylbenzyl, trimethylbenzyl, t-butylbenzyl or 2-phenylethyl. Benzyl is preferred.

Acyl R₁ containing not more than 8 carbon atoms can be an aliphatic or aromatic group. Representative examples are formyl, acetyl, propionyl, butyryl, pentanoyl, hexanoyl, heptanoyl, octanoyl, benzoyl, acryloyl or crotonyl. C₁ -C₈ alkanoyl, C₃ -C₈ alkenoyl and benzoyl are preferred. Acetyl is especially preferred.

Examples of compounds of the formula (I) wherein the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR9## are ##STR10##

The preferred definitions of R₁ are hydrogen, C₁ -C₄ alkyl, OH, C₆ -C₁₂ alkoxy, C₅ -C₈ cycloalkoxy, allyl, benzyl or acetyl, in particular hydrogen or methyl.

Those compounds of the formula (I) are preferred in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) in which R₂ is hydrogen, C₁ -C₁₂ alkyl, C₂ -C₃ alkyl substituted in the 2- or 3-position by C₁ -C₄ alkoxy, by di(C₁ -C₄ alkyl)amino or by a 1-pyrrolidyl, 1-piperidyl or 4-morpholinyl group; C₅ -C₈ cycloalkyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl; benzyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl; tetrahydrofurfuryl or a group of the formula (III), or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR11## with R being a group of the formula (III).

Those compounds of the formula (I) are particularly preferred in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) in which R₂ is hydrogen, C₁ -C₁₀ alkyl, C₂ -C₃ alkyl substituted in the 2- or 3-position by methoxy, by ethoxy, by dimethylamino, by diethylamino or by 4-morpholinyl; cyclohexyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl; benzyl, tetrahydrofurfuryl or a group of the formula (HI), or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR12## with R being a group of the formula (III).

Those compounds of the formula (I) are of special interest in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) in which R₂ is hydrogen, C₁ -C₈ alkyl, cyclohexyl, benzyl or a group of the formula (III), or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR13## with R being a group of the formula (III).

Those compounds of the formula (I) are of particular interest in which X and Y are a group of the formula (IIa) or (IIb) in which R₁ is hydrogen or methyl, R₂ is hydrogen or C₁ -C₄ alkyl, or the two radicals X and the two radicals Y, each, form together a group ##STR14## with R being a group of the formula (III).

Examples of particularly preferred compounds of the formula (I) are those of the formulae ##STR15##

The compounds of the formula (I) can be prepared by processes known per se, for example, starting from tetrahydrofuran-2,3,4,5-tetracarboxylic acid or esters thereof with C₁ -C₄ alkanols, or from the corresponding dianhydride.

In particular, if X and Y are groups of the formulae (IIa) and (IIb), the compounds of the formula (I) can be prepared e.g. by reacting a C₁ -C₄ alkyl ester of tetrahydrofuran-2,3,4,5-tetracarboxylic acid with compounds of the formula (IVa) or (IVb) ##STR16## in the appropriate molar ratios, preferably with an excess over theory, in the presence of catalytic quantities of e.g. an alkoxide of Ti(IV) or of a hydride, alkoxide or amide of Li, Na or K.

Such reactions can be carried out without a solvent or in an organic solvent, for example toluene or xylene, operating at temperatures from e.g. 100° to 200° C., preferably 120° to 180° C.

For the preparation of compounds of the formula (I) wherein the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR17## with R being a group of the formula (III), it is preferable to react, in two stages, the dianhydride of tetrahydrofuran-2,3,4,5-tetracarboxylic acid with 2 mol of a compound of the formula (V) ##STR18##

In a first phase, operating in dimethylformamide at temperatures from e.g. 0° to 60° C., preferably 20° to 40° C., a bis(semiamide) is formed as an intermediate which, in a further reaction, is cyclised to form the diimide by heating with acetic anhydride and triethylamine at temperatures from e.g. 50° to 150° C., preferably from 70° to 120° C.

Tetrahydrofuran-2,3,4,5-tetracarboxylic acid and the corresponding dianhydride are commercially available; the corresponding tetraesters and also the compounds of the formula (IVa), (IVb) and (V) can easily be prepared by known processes.

As mentioned at the outset, the compounds of the formula (I) are highly effective in improving the light stability, heat stability and oxidation stability of organic materials, in particular synthetic polymers and copolymers.

Examples of such organic materials which can be stabilised are:

1. Polymers of monoolefins and diolefins, for example polypropylene, polyisobutylene, polybutene-1, polymethylpentene-1, polyisoprene or polybutadiene, as well as polymers of cycloolefins, for instance of cyclopentene or norbornene, polyethylene (which optionally can be crosslinked), for example high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), branched low density polyethylene (BLDPE).

2. Mixtures of the polymers mentioned under 1), for example mixtures of polypropylene with polyisobutylene, polypropylene with polyethylene (for example PP/HDPE, PP/LDPE) and mixtures of different types of polyethylene (for example LDPE/HDPE).

3. Copolymers of monoolefines and diolefines with each other or with other vinyl monomers, such as, for example, ethylene/propylene, linear low density polyethylene (LLDPE) and its mixtures with low density polyethylene (LDPE), propylene/butene-1, ethylene/hexene, ethylene/ethylpentene, ethylene/heptene, ethylene/octene, propylene/isobutylene, ethylene/butene-1, propylene/butadiene, isobutylene/isoprene, ethylene/alkyl acrylates, ethylene/alkyl methacrylates, ethylene/vinyl acetate copolymers and their copolymers with carbon monoxide or ethylene/acrylic acid copolymers and their salts (ionomers) and terpolymers of ethylene with propylene and a diene, such as hexadiene, dicyclopentadiene or ethylidene-norbornene; as well as mixtures of such copolymers and their mixtures with polymers mentioned in 1) above, for example polypropylene/ethylene-propylene-copolymers, LDPE/ethylene-vinyl acetate copolymers (EVA), LDPE/ethylene-acrylic acid copolymers (EAA), LLDPE/EVA, LLDPE/EAA and statistical or alternating polyalkylene/carbon monoxide-copolymers as well as their mixtures with other polymers, for example polyamide.

3a. Hydrocarbon resins (for example C₅ -C₉) and hydrogenated modifications thereof (for example tackyfiers) and mixtures of polyalkylenes and starch.

4. Polystyrene, poly-(p-methylstyrene), poly-(α-methylstyrene).

5. Copolymers of styrene or α-methylstyrene with dienes or acrylic derivatives, such as, for example, styrene/butadiene, styrene/acrylonitrile, styrene/alkyl methacrylate, styrene/maleic anhydride, styrene/butadiene/alkyl acrylate, styrene/butadiene/alkyl methacrylate styrene/acrylonitrile/methyl acrylate; mixtures of high impact strength from styrene copolymers and another polymer, such as, for example, from a polyacrylate, a diene polymer or an ethylene/propylene/diene terpolymer; and block copolymers of styrene, such as, for example, styrene/butadiene/styrene, styrene/isoprene/styrene, styrene/ethylene/butylene/styrene or styrene/ethylene/propylene/styrene.

6. Graft copolymers of styrene or α-methylstyrene such as, for example, styrene on polybutadiene, styrene on polybutadiene-styrene or polybutadiene-acrylonitrile; styrene and acrylonitrile (or methacrylonitrile) on polybutadiene; styrene and maleic anhydride or maleimide on polybutadiene; styrene, acrylonitrile and maleic anhydride or maleimide on polybutadiene; styrene, acrylonitrile and methyl methacrylate on polybutadiene, styrene and alkyl acrylates or methacrylates on polybutadiene, styrene and acrylonitrile on ethylene/propylene/diene terpolymers, styrene and acrylonitrile on polyacrylates or polymethacrylates, styrene and acrylonitrile on acrylate/butadiene copolymers, as well as mixtures thereof with the copolymers listed under 5), for instance the copolymer mixtures known as ABS-, MBS-, ASA- or AES-polymers.

7. Halogen-containing polymers, such as polychloroprene, chlorinated rubbers, chlorinated or sulfochlorinated polyethylene, copolymers of ethylene and chlorinated ethylene, epichlorohydrin homo- and copolymers, polymers from halogen-containing vinyl compounds,as for example, poly- vinylchloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, as well as copolymers thereof, as for example, vinyl chloride/vinylidene chloride, vinyl chloride/vinyl acetate or vinylidene chloride/vinyl acetate copolymers.

8. Polymers which are derived from α,β-unsaturated acids and derivatives thereof, such as polyacrylates and polymethacrylates, with butyl acrylate impact resistant modified polymethyl methacrylate, polyacrylamide and polyacrylonitrile.

9. Copolymers from the monomers mentioned under 8) with each other or with other unsaturated monomers, such as, for instance, acrylonitrile/butadiene, acrylonitrile/alkyl acrylate, acrylonitrile/alkoxyalkyl acrylate or acrylonitrile/vinyl halogenide copolymers or acrylonitrile/alkyl methacrylate/butadiene terpolymers.

10. Polymers which are derived from unsaturated alcohols and amines, or acyl derivatives thereof or acetals thereof, such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, polyvinyl maleate, polyvinyl butyral, polyallyl phthalate or polyallylmelamine; as well as their copolymers with olefins mentioned in 1) above.

11. Homopolymers and copolymers of cyclic ethers, such as polyalkylene glycols, polyethylene oxide, polypropylene oxide or copolymers thereof with bis-glycidyl ethers.

12. Polyacetals, such as polyoxymethylene and those polyoxymethylenes which contain ethylene oxide as a comonomer; polyacetals modified with thermoplastic polyurethanes, acrylates or MBS.

13. Polyphenylene oxides and sulfides, and mixtures of polyphenylene oxides with polystyrene or polyamides.

14. Polyurethanes which are derived from polyethers, polyesters or polybutadienes with terminal hydroxyl groups on the one side and aliphatic or aromatic polyisocyanates on the other side, as well as precursors thereof (polyisocyanates, polyols or prepolymers).

15. Polyamides and copolyamides which are derived from diamines and dicarboxylic acids and/or from aminocarboxylic acids or the corresponding lactams, such as polyamide 4, polyamide 6, polyamide 6/6, 6/10, 6/9, 6/12, 4/6, 12/12 polyamide 11, polyamide 12, aromatic polyamides obtained by condensation of m-xylene diamine and adipic acid; polyamides prepared from hexamethylenediamine and isophthalic or/and terephthalic acid and optionally an elastomer as modifier, for example poly-2,4,4,-trimethylhexamethylene terephthalamide or poly-m-phenylene isophthalamide. Further copolymers of the aforementioned polyamides with polyolefins, olefin copolymers, ionomers or chemically bonded or grafted elastomers; or with polyethers, such as for instance, with polyethylene glycols, polypropylene glycols or polytetramethylene glycols. Polyamides or copolyamides modified with EPDM or ABS. Polyamides condensed during processing (RIM-polyamide systems).

16. Polyureas, polyimides and polyamide-imides.

17. Polyesters which are derived from dicarboxylic acids and diols and[ch]or from hydroxycarboxylic acids or the corresponding lactones, such as polyethylene terephthalate, polybutylene terephthalate, poly-1,4-dimethylolcyclohexane terephthalate, poly-[2,2,-(4-hydroxyphenyl)-propane] terephthalate and polyhydroxybenzoates as well as block-copolyether-esters derived from polyethers having hydroxyl end groups.

18. Polycarbonates and polyester-carbonates.

19. Polysulfones, polyether-sulfones and polyether-ketones.

20. Crosslinked polymers which are derived from aldehydes on the one hand and phenols, ureas and melamines on the other hand, such as phenol/formaldehyde resins, urea/formaldehyde resins and melamine/formaldehyde resins.

21. Drying and non-drying alkyd resins.

22. Unsaturated polyester resins which are derived from copolyesters of saturated and unsaturated dicarboxylic acids with polyhydric alcohols and vinyl compounds as crosslinking agents, and also halogen-containing modifications thereof of low inflammability.

23. Thermosetting acrylic resins, derived from substituted acrylic esters, such as epoxy-acrylates, urethane-acrylates or polyester-acrylates.

24. Alkyd resins, polyester resins or acrylate resins in admixture with melamine resins, urea resins, polyisocyanates or epoxide resins as crosslinking agents.

25. Crosslinked epoxide resins which are derived from polyepoxides, for example from bis-glycidyl ethers or from cycloaliphatic diepoxides.

26. Natural polymers, such as cellulose, rubber, gelatine and derivatives thereof which are chemically modified in a polymer-homologous manner, such as cellulose acetates, cellulose propionates and cellulose butyrates, or the cellulose ethers, such as methylcellulose; rosins and their derivatives.

27. Mixtures of polymers as mentioned above, for example PP/EPDM, Polyamide 6/EPDM or ABS, PVC/EVA, PVC/ABS, PVC/MBS, PC/ABS, PBTP/ABS, PC/ASA, PC/PBT, PVC/CPE, PVC/acrylates, POM/thermoplastic PUR, PC/thermoplastic PUR, POM/acrylate, POM/MBS, PPE/HIPS, PPF/PA 6.6 and copolymers, PA/HDPE, PA/PP, PA/PPE.

28. Naturally occurring and synthetic organic materials which are pure monomeric compounds or mixtures of such compounds, for example mineral oils, animal and vegetable fats, oil and waxes, or oils, fats and waxes based on synthetic esters (e.g. phthalates, adipates, phosphates or trimellithates) and also mixtures of synthetic esters with mineral oils in any weight ratios, which materials may be used as plasticizer for polymers or as textile spinning oils, as well as aqueous emulsions of such materials.

29. Aqueous emulsions of natural or synthetic rubber, e.g. natural latex or latices of carboxylated styrene/butadiene copolymers.

The compounds of the formula (I) are particularly suitable for improving the light stability, heat stability and oxidation stability of polyolefins, especially polyethylene and polypropylene.

The compounds of the formula (I) can be used in mixtures with organic materials in various proportions depending on the nature of the material to be stabilized, on the end use and on the presence of other additives.

In general, it is appropriate to use, for example, 0.01 to 5% by weight of the compounds of the formula (I), relative to the weight of the material to be stabilized, preferably 0.05 to 1%.

In general, the compounds of the formula (I) can be added to the polymeric materials before, during or after the polymerization or crosslinking of the said materials.

The compounds of the formula (I) can be incorporated in the pure form or encapsulated in waxes, oils or polymers into the polymeric materials.

The compounds of the formula (I) can be incorporated in the polymeric materials by various processes, such as dry mixing in the form of powder, or wet mixing in the form of solutions or suspensions or also in the form of a masterbatch; in such operations, the polymer can be used in the form of powder, granules, solutions, suspensions or in the form of latices.

The materials stabilized with the products of the formula (I) can be used for the production of mouldings, films, tapes, monofilaments, fibres, surface coatings and the like.

If desired, other conventional additives for synthetic polymers, such as antioxidants, UV absorbers, nickel stabilizers, pigments, fillers, plasticizers, antistatic agents, flameproofing agents, lubricants, corrosion inhibitors and metal deactivators, can be added to the mixtures of the compounds of the formula (I) with the organic materials.

Particular examples of additives which can be used in admixture with the compounds of the formula (I) are:

1. Antioxidants

1.1. Alkylated monophenols, for example 2,6-di-tert-butyl-4-methyl-phenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-iso-butylphenol, 2,6-dicyclopentyl-4-methylphenol, 2-(α-methylcyclohexyl)-4,6-dimethylphenol, 2,6-dioctadecyl-4-methylphenol, 2,4,6-tri-cyclohexyl-phenol, 2,6-di-tert-butyl-4-methoxymethylphenol, 2,6-di-nonyl-4-methylphenol, 2,4-dimethyl-6-(1'-methyl-undec-1'-yl)-phenol, 2,4-dimethyl-6-(1'-methyl-heptadec-1'-yl)-phenol, 2,4-dimethyl-6-(1'-methyl-tridec-1'-yl)-phenol and mixtures therof.

1.2. Alkylthiomethylphenols, for example 2,4-dioctylthiomethyl-6-tert-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-di-dodecylthiomethyl-4-nonylphenol.

1.3. Hydroquinones and alkylated hydroquinones, for example 2,6-di-tert-butyl-4-methoxy-phenol, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, 2,6-di-phenyl-4-octadecyloxyphenol, 2,6-di-tert-butyl-hydroquinone, 2,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenyl-stearate, bis-(3,5-di-tert-butyl-4-hydroxyphenyl)adipate.

1.4. Hydroxylated thiodiphenyl ethers, for example 2,2'-thiobis(6-tert-butyl-4-methylphenol), 2,2'-thiobis(4-octylphenol), 4,4'-thiobis(6-tert-butyl-3-methylphenol), 4,4'-thiobis(6-tert-butyl-2-methylphenol), 4,4'-thio-bis-(3,6-di-sec-amylphenol), 4,4'-bis-(2,6-dimethyl-4-hydroxyphenyl)-disulfide.

1.5. Alkylidenebisphenols, for example 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), 2,2'-methylenebis[4-methyl-6-(α-methylcyclohexyl)phenol], 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(6-nonyl-4-methylphenol), 2,2'-methylenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(6-tert-butyl-4-isobutylphenol), 2,2'-methylenebis[6-(α-methylbenzyl)-4-nonylphenol], 2,2'-methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol], 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-methylenebis(6-tert-butyl-2-methylphenol), 1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)butane 2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol, 1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 1,1-bis(5-tert-butyl-4-hydroxy-2-methyl-phenyl)-3-n-dodecylmercaptobutane, ethylene glycol bis[3,3-bis(3'-tert-butyl-4'-hydroxyphenyl)butyrate], bis(3-tert-butyl-4-hydroxy-5-methylphenyl)dicyclopentadiene, bis[2-(3'-tert-butyl-2'-hydroxy-5'-methylbenzyl)-6-tert-butyl-4-methylphenyl]terephthalate, 1,1-bis-(3,5-dimethyl-2-hydroxyphenyl)butan, 2,2-bis-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propan, 2,2-bis-(5-tert.-butyl-4-hydroxy-2-methylphenyl)-4-n-dodecylmercapto-butan, 1,1,5,5-tetra-(5-tert.-butyl-4-hydroxy-2-methylphenyl)-pentan.

1.6. O--, N-- and S-benzyl compounds, for example 3,5,3',5'-tetra-tert.-butyl-4,4'-dihydroxydibenzylether, octadecyl-4-hydroxy-3,5-dimethylbenzyl-mercaptoacetate, tris-(3,5-di-tert.-butyl-4-hydroxybenzyl)-amine, bis-(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)dithioterephthalate, bis-(3,5-di-tert.-butyl-4-hydroxybenzyl)-sulfide, isooctyl-3,5-di-tert.-butyl-4-hydroxybenzyl-mercaptoacetate.

1.7. Hydroxybenzylated Malonates, for example dioctadecyl-2,2-bis-(3,5-di-tert.-butyl-2-hydroxybenzyl)-malonate, di-octadecyl-2-(3-tert.-butyl-4-hydroxy-5-methylbenzyl)-malonate, di-dodecylmercaptoethyl-2,2-bis-(3,5-di-tert.-butyl-4-hydroxybenzyl)-malonate, Di-[4-(1,1,3,3-tetramethylbutyl)-phenyl]-2,2-bis-(3,5-di-tert.-butyl-4-hydroxybenzyl)-malonate.

1.8. Hydroxybenzyl-Aromatics, for example 1,3,5-tris-(3,5-di-tert.-butyl-4-hydroxy-benzyl)-2,4,6-trimethylbenzene, 1,4-bis-(3,5-di-tert.-butyl-4-hydroxybenzyl)-2,3,5,6-tetramethylbenzene, 2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxybenzyl )-phenol.

1.9. Triazine Compounds, for example 2,4-bis-octylmercapto-6-(3,5-di-tert.-butyl-4-hydroxyanilino)-1,3,5-triazine, 2-octylmercapto-4,6-bis-(3,5-di-tert.-butyl-4-hydroxyanilino)-1,3,5-triazine, 2-octylmercapto-4,6-bis-(3,5-di-tert.-butyl-4-hydroxyphenoxy)-1,3,5-triazine, 2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxyphenoxy)-1,2,3-triazine, 1,3,5-tris-(3,5-di-tert.-butyl-4-hydroxybenzyl)-isocyanurate, 1,3,5-tris-(4-tert.-butyl-3-hydroxy-2,6-di-methylbenzyl)-isocyanurate, 2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxyphenylethyl)-1,3,5-triazine, 1,3,5-tris-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)-hexahydro-1,3,5-triazine, 1,3,5-tris-(3,5-dicyclohexyl-4-hydroxybenzyl)-isocyanurate.

1.10. Benzylphosphonates, for example dimethyl-2,5-di-tert.-butyl-4-hydroxybenzylphosphonate, diethyl-3,5-di-tert.-butyl-4-hydroxybenzylphosphonate, dioctadecyl-3,5-di-tert.-butyl-4-hydroxybenzylphosphonate, dioctadecyl-5-tert.-butyl-4-hydroxy-3-methylbenzylphosphonate, Ca-salt of the 3,5-di-tert.-butyl-4-hydroxybenzyl-phosphonic acid monoethylester.

1.11. Acylaminophenols, for example lauric acid 4-hydroxyanilide, stearic acid 4-hydroxyanilide, octyl N-(3,5-di-tert-butyl-4-hydroxyphenyl)-carbamate.

1.12. Esters of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl) isocyanurate, N,N'-bis(hydroxyethyl)oxalic acid diamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]-octane.

1.13. Esters of β-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl) isocyanurate, N,N'-bis(hydroxyethyl)oxalic acid diamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.21-octane.

1.14 Esters of β-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl) isocyanurate, N,N'-bis(hydroxyethyl)oxalic acid diamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2-octane.

1.15 Esters of 3,5-di-tert.-butyl-4-hydroxyphenyl acetic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl) isocyanurate, N,N'-bis(hydroxyethyl)oxalic acid diamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]-octane.

1.16. Amides of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid e.g. N,N'-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hexamethylene-diamine, N,N'-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)tri-methylene-diamine, N,N'-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)-hydrazine.

2. UV absorbers and light stabilisers

2.1. 2-(2'-Hydroxyphenyl)benzotriazoles, for example the 5'-methyl, 3',5'-di-tert-butyl, 5'-tert-butyl, 5'-(1,1,3,3-tetramethylbutyl), 5-chloro-3',5'-di-tert-butyl, 5-chloro-3'-tert-butyl-5'-methyl, 3'-sec-butyl-5'-tert-butyl, 4'-octoxy, 3',5'-di-tert-amyl and 3',5'-bis(α,α-dimethylbenzyl), mixture of 5-chloro-3'-tert.-butyl-5'-(2-octyloxycarbonylethyl)-and 5-chloro-3'-tert.-butyl-5'-[2-(2-ethylhexyloxy)-carbonylethyl]-, 5-chloro-3'-tert.-butyl-5'-(2-methoxycarbonylethyl)-, 3'-tert.-butyl-5'-(2-methoxycarbonylethyl)-, 3'-tert.-butyl-5'-(2-octyloxycarbonylethyl)-, 3'-tert.-butyl-5'-[2-(2-ethylhexyloxy)carbonylethyl]-, 3'-dodecyl-5'-methyl- and 3'-tert.-butyl-5'-(2-isooctyloxycarbonylethyl)-2'-hydroxyphenyl-2H-benztriazole(2), 2,2'-methylene-bis[4-(1,1,3,3-tetramethylbutyl)-6-benztriazole-2-yl-phenol]; product of ester interchange of 2-[3'-tert.-butyl-5'-(2-methoxycarbonylethyl)-2'-hydroxy-phenyl]-2H-benztriazole with polyethylene glycol 300; [R--CH₂ CH₂ --COO(CH₂)₃ ]₂ -- with R=3'-tert.-butyl-4'-hydroxy-5'-2H-benzotriazole-2-yl-phenyl.

2.2.2-Hydroxybenzophenones, for example the 4-hydroxy, 4-methoxy, 4-octoxy, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2',4'-trihydroxy and 2'-hydroxy-4,4'-dimethoxy derivatives.

2.3. Esters of substituted and unsubstituted benzoic acids, as for example 4-tert.butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoylresorcinol, bis-(4-tert.butylbenzoyl)-resorcinol, benzoylresorcinol, 2,4-di-tert.butylphenyl 3,5-di-tert.butyl-4-hydroxybenzoate, hexadecyl 3,5-di-tert.butyl-4-hydroxybenzoate, octadecyl 3,5-di-tert.-butyl-4-hydroxybenzoate, 2 methyl-4,6-di-tert.-butylphenyl 3,5-di-tert.-butyl-4-hydroxybenzoate.

2.4. Acrylates, for example ethyl α-cyano-β,β-diphenylacrylate, isooctyl α-cyano-β,β-diphenylacrylate, methyl α-carbomethoxycinnamate, methyl α-cyano-β-methyl-p-methoxy-cinnamate, butyl α-cyano-β-methyl-p-methoxy-cinnamate, methyl α-carbomethoxy-p-methoxycinnamate and N-(β-carbomethoxy-β-cyanovinyl)-2-methylindoline.

2.5. Nickel compounds, for example nickel complexes of 2,2'-thio-bis-[4-(1,1,3,3-tetramethylbutyl)phenol], such as the 1:1 or 1:2 complex, with or without additional ligands such as n-butylamine, triethanolamine or N-cyclohexyldiethanolamine, nickel dibutyldithiocarbamate, nickel salts of 4-hydroxy-3,5-di-tert-butylbenzyl-phosphonic acid monoalkyl esters, e.g. of the methyl or ethyl ester, nickel complexes of ketoximes, e.g. of 2-hydroxy-4-methyl-phenyl undecyl ketoxime, nickel complexes of 1-phenyl-4-lauroyl-5-hydroxypyrazole, with or without additional ligands.

2.6. Sterically hindered amines, for example bis(2,2,6,6-tetramethyl-piperidyl) sebacate, bis-(2,2,6,6-tetramethyl-piperidyl) succinate, bis(1,2,2,6,6-pentamethylpiperidyl) sebacate, bis(1,2,2,6,6-pentamethylpiperidyl) n-butyl-3,5-di-tert-butyl-4-hydroxy-benzylmalonate, the condensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, the condensation product of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylenediamine and 4-tert-octylamino-2,6-dichloro-1,3,5-triazine, tris(2,2,6,6-tetramethyl-4-piperidyl) nitrilotriacetate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane-tetracarboxylate, 1,1'-(1,2-ethanediyl)bis-(3,3,5,5-tetramethylpiperazinone), 4-benzoyl-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, bis-(1,2,2,6,6-pentamethylpiperidyl)-2-n-butyl-2-(2-hydroxy-3,5-di-tert.-butylbenzyl) malonate, 3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazasprio[4.5]decan-2,4-dion, bis-(1-octyloxy-2,2,6,6-tetramethylpiperidyl) sebacate, bis-(1-octyloxy-2,2,6,6-tetramethylpiperidyl) succinate, product of condensation of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylene diamine and 4-morpholino-2,6-dichloro-1,3,5-triazine, product of condensation of-chloro-4,6-di-(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-1,3,5-triazine and 1,2-bis-(3-aminopropylamino)ethane, product of condensation of 2-chloro-4,6-di-(4-n-butylamino-1,2,2,6,6-pentamethylpiperidyl)-1,3,5-triazine and 1,2-bis-(3-aminopropylamino )ethane, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dion, 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidin-2,5-dion, 3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidyl)-pyrrolidin-2,5-dion.

2.7. Oxalic acid diamides, for example 4,4'-dioctyloxyoxanilide, 2,2'-dioctyloxy-5,5'-di-tert-butyloxanilide, 2,2'-didodecyloxy-5,5'-di-tert-butyloxanilide, 2-ethoxy-2'-ethyloxanilide, N,N'-bis(3-dimethylamino-propyl)oxalamide, 2-ethoxy-5-tert-butyl-2'-ethyloxanilide and its mixture with 2-ethoxy-2'-ethyl-5,4'-di-tert-butyloxanilide and mixtures of ortho- and para-methoxy-disubstituted oxanilides and mixtures of o- and p-ethoxy-disubstituted oxanilides.

2.8.2-(2-Hydroxyphenyl)-1,3,5-triazines, for example 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-octyloxy-phenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-(2,4-dihydroxy-phenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2-hydroxy-4-propyloxyphenyl)-6-(2,4-dimethylphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(4-methylphenyl)-1,3,5-triazine, 2-(2-hydroxy4-dodecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3-butyloxy-propyloxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3-octyloxy-propyloxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine.

3. Metal deactivators, for example N,N'-diphenyloxalic acid diamide, N-salicylal-N'-salicyloylhydrazine, N,N'-bis(salicyloyl)hydrazine, N,N'-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazine, 3-salicyl-oylamino-1,2,4-triazole, bis(benzylidene)oxalodihydrazide, Oxanilide, isophthalic acid dihydrazide, sebacic acid-bis-phenylhydrazide, N,N'-diacetal-adipinic acid dihydrazide, N,N'-bis-salicyloyl-oxalic acid dihydrazide, N,N'-bis-salicyloyl-thiopropionic acid dihydrazide.

4. Phosphites and phosphonites, for example triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diiso-decyl pentaerythritol diphosphite, bis(2,4-di-tert.-butylphenyl) pentaerythritol diphosphite, bis-(2,6-di-tert.-butyl-4-methylphenyl)-pentaerythritol diphosphite, bis-isodecyloxy-pentaerythritol diphosphite, bis-(2,4-di-tert.-butyl-6-methylphenyl)-pentaerythritol diphosphite, bis-(2,4,6-tri-tert.-butylphenyl)-pentaerythritol diphsophite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4'-biphenylene diphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert.-butyl-12H-dibenz[d,g]-1,3,2-dioxaphosphocin, 6-fluoro-2,4,8,10-tetra-tert.-butyl-12-methyl-dibenz[d,g]-1,3,2-dioxaphosphocin.

4a. Hydroxylamines, for example dibenzylhydroxylamine, dioctylhydroxylamine, didodecylhydroxylamine, ditetradecylhydroxylamine, dihexadecylhydroxylamine, dioctadecylhydroxylamine, 1-hydroxy-2,2,6,6-tetramethyl-4-piperidyl benzoate or bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate.

5. Peroxide scavengers, for example esters of β-thiodipropionic acid, for example the lauryl, stearyl, myristyl or tridecyl esters, mercaptobenzimidazole or the zinc salt of 2-mercaptobenzimidazole, zinc dibutyldithiocarbamate, dioctadecyl disulfide, pentaerythritol tetrakis(β-dodecyl-mercapto)propionate.

6. Polyamide stabilisers, for example, copper salts in combination with iodides and/or phosphorus compounds and salts of divalent manganese.

7. Basic co-stabilisers, for example, melamine, polyvinylpyrrolidone, dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamides, polyurethanes, alkali metal salts and alkaline earth metal salts of higher fatty acids for example Ca stearate, Zn stearate, Mg behenate, Mg stearate, Na ricinoleate and K palmirate, antimony pyrocatecholate or zinc pyrocatecholate.

8. Nucleating agents, for example, 4-tert.butyl-benzoic acid, adipic acid, diphenylacetic acid.

9. Fillers and reinforcing agents, for example, calcium carbonate, silicates, glass fibres, asbestos, talc, kaolin, mica, barium sulfate, metal oxides and hydroxydes, carbon black, graphite.

10. Other additives, for example, plasticisers, lubricants, emulsifiers, pigments, optical brighteners, flameproofing agents, antistatic agents and blowing agents.

The compounds of the formula (I) can also be used as stabilisers, especially as light stabilisers, for almost all materials known in the art of photographic reproduction and other reproduction techniques as e.g. described in Research Disclosure 1990, 31429 (pages 474 to 480).

Several examples of the preparation and use of the compounds of the formula (I) are reported for more detailed illustration of the present invention; these examples are given solely for illustrative purposes and do not imply any restriction.

EXAMPLE 1

Preparation of the compound of the formula ##STR19##

A solution containing 35.4 g (0.075 mol) of butyl tetrahydrofuran-2,3,4,5-tetracarboxylate, 50.3 g (0.32 mol) of 2,2,6,6-tetramethyl-4-piperidinole and 1 ml of titanium(IV) isopropoxide in 200 ml of toluene is heated under reflux for 6 hours, the solvent and the butanol set free during the reaction being slowly distilled off.

After cooling to ambient temperature, the reaction mixture is diluted with 100 ml of toluene, washed with water and dehydrated over Na₂ SO₄.

The solvent is then removed in vacuo and the residue is crystallised from isopropyl ether. The product obtained has a melting point of 62°-64° C.

Analysis for C₄₄ H₇₆ N₄ O₉ : Calculated: C=65.64%; H=9.51%; N=6.96% Found: C=65.47%; H=9.51%; N=6.93%

EXAMPLE 2

Following the procedure described in Example 1, but using 1,2,2,6,6-pentamethyl-4-piperidinol in place of 2,2,6,6-tetramethyl-4-piperidinole, the compound of the formula ##STR20## of melting point 140°-142° C. (from a 4:1 acetonitrile/water mixture) is obtained.

Analysis for C₄₈ H₈₄ N₄ O₉ : Calculated: C=66.94%; H=9.83%; N=6.51% Found: C=66.86%; H=9.77%; N=6.45%

EXAMPLE 3:

Preparation of the compound of the formula ##STR21##

A mixture containing 35.4 g (0.075 mol) of butyl tetrahydrofuran-2,3,4,5-tetracarboxylate, 93.8 g (0.6 mol) of 2,2,6,6-tetramethyl-4-piperidineamine and 1 ml of titanium(IV) isopropoxide is heated for 8 hours at 130° C., the butanol formed during the reaction being removed.

After cooling to ambient temperature, 70 ml of dichloromethane are added, and the mixture is heated under reflux for a few minutes.

As a result of cooling, a precipitate forms which is separated off by filtration and then washed with 100 ml of acetonitrile and crystallised from toluene. The product obtained has a melting point of 250°-252° C.

Analysis for C₄₄ H₈₀ N₈ O₅ : Calculated: C=65.96%; H=10.06%; N=13.99% Found: C=65.72%; H=10.01%; N=13.83%

EXAMPLE 4

Following the procedure described in Example 3, but using 1,2,2,6,6-pentamethyl-4-piperidineamine instead of the 2,2,6,6-tetramethyl-4-piperidineamine, the compound of the formula ##STR22## of melting point 242°-244° C. (from hexane) is obtained.

Analysis for C₄₈ H₈₈ N₈ O5: Calculated: C=67.25%; H=10.35%; N=13.07% Found: C=66.98%; H=10.34%; N=13.04%

EXAMPLE 5

Preparation of the compound of the formula ##STR23## 31.3 g (0.2 mol) of 2,2,6,6-tetramethyl-4-piperidineamine are added in the course of 1 hour to a solution of 21.2 g (0.1 mol) of the dianhydride of tetrahydrofuran-2,3,4,5-tetracarboxylic acid in 150 ml of dimethylformamide, without exceeding 35° C.

After the end of the addition, the mixture is stirred for 2 hours at ambient temperature, and the precipitate formed is separated off by filtration and washed with acetone. 400 ml of acetic anhydride and 40.5 g (0.4 mol) of triethylamine are added to the product, and the mixture is heated for 5 hours at 75° C.

During the reaction, a precipitate forms which, after cooling to ambient temperature, is separated off by filtration, washed with acetone and finally crystallised from dimethylformamide. The product obtained has a melting point of >310° C.

Analysis for C₂₆ H₄₀ N₄ O₅ : Calculated: C=63.91%; H=8.25%; N=11.47% Found: C=63.53%; H=8.12%; N=11.29%

EXAMPLE 6

Light-stabilising action in polypropylene tapes. 1 g of each of the compounds indicated in Table 1, 1 g of tris(2,4-di-t-butylphenyl) phosphite, 0.5 g of pentaerythritol tetrakis-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 1 g of calcium stearate are mixed in a slow mixter with 1000 g of polypropylene powder of melt index=2 g/10 minutes (measured at 230° C. and 2.16 kg).

The mixtures are extruded at 200°-220° C. to give polymer granules which are then converted into stretched tapes with a thickness of 50 μm and a width of 2.5 mm, using a pilot-type apparatus (®Leonard-Sumirago (VA) Italy) operating under the following conditions:

Extruder temperature: 210°-230° C.

Head temperature: 240°-260° C.

Stretch ratio: 1:6

The tapes thus prepared are exposed, mounted on a white card, in a 65 WR Weather-O-Meter (ASTM D2565-85) with a black panel temperature of 63° C.

The residual tenacity is measured on samples taken after various times of exposure to light by means of a constant-speed tensometer; the exposure time in hours (T₅₀) needed to halve the initial tenacity is then calculated.

Tapes prepared under the same conditions as indicated above, but without the addition of compounds of the present invention, are exposed for comparison. Table 1 gives the results obtained.

                  TABLE 1                                                          ______________________________________                                         Stabiliser          T.sub.50 (hours)                                           ______________________________________                                         without stabiliser   440                                                       Compound from Example 1                                                                            3150                                                       Compound from Example 2                                                                            3480                                                       ______________________________________                                    

EXAMPLE 7

Antioxidant action in polypropylene plaques. 1 g of the compound indicated in Table 2, 0.5 g of octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate 1 g of tris(2,4-di-t-butylphenyl) phosphite and 1 g of calcium stearate are mixed in a slow mixer with 1000 g of polypropylene powder of melt index=2.1 g/10 minutes (measured at 230° C. and 2.16 kg).

The mixtures are extruded twice at 200°-220° C. to give polymer granules which are then converted into plaques of 1 mm thickness by compression-moulding for 6 minutes at 230° C.

The plaques are then punched by means of a DIN 53451 mould, and the specimens obtained are exposed in a forced-circulation air oven maintained at a temperature of 135° C.

The specimens are tested at intervals by folding them by 180°, in order to determine the time (in hours) needed to cause fracture.

Specimens prepared under the same conditions as indicated above, but without addition of compounds of the present invention, are exposed for comparison. The results obtained are shown in Table 2.

                  TABLE 2                                                          ______________________________________                                         Stabiliser        Time to fracture (in hours)                                  ______________________________________                                         without stabiliser                                                                                600                                                         Compound from Example 2                                                                          1760                                                         ______________________________________                                     

What is claimed is:
 1. A compound of formula (I) ##STR24## in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) ##STR25## in which R₁ is hydrogen, C₁ -C₈ alkyl, O, OH, NO, CH₂ CN, C₁ -C₁₈ alkoxy, C₅ -C₁₂ cycloalkoxy, C₃ -C₆ alkenyl, C₇ -C₉ phenylalkyl which is unsubstituted or mono-, di- or tri-substituted on the phenyl by C₁ -C₄ alkyl; or C₁ -C₈ acyl;R₂ is hydrogen, C₁ -C₁₈ alkyl, C₃ -C₆ alkenyl, C₂ -C₄ alkyl substituted in the 2-, 3- or 4-position by C₁ -C₈ alkoxy, by di(C₁ -C₄ alkyl)amino or by a 5- to 7-membered nitrogen-containing heterocyclic group with the free valency on the nitrogen atom; C₅ -C₁₂ cycloalkyl which is unsubstituted or mono-, di- or tri-substituted by C₁ C₄ alkyl; C₇ -C₉ phenylalkyl which is unsubstituted or mono-, di- or tri-substituted on the phenyl by C₁ -C₄ alkyl; tetrahydrofurfuryl or a group of the formula (III) ##STR26## with R₁ being as defined above; or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR27## with R being a group of the formula (III).
 2. A compound of the formula (I) according to claim 1, in which R₁ is hydrogen, C₁ -C₄ alkyl, OH, C₆ -C₁₂ alkoxy, C₅ -C₈ cycloalkoxy, allyl, benzyl or acetyl.
 3. A compound of the formula (I) according to claim 1, in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) in which R₂ is hydrogen, C₁ -C₁₂ alkyl, C₂ -C₃ alkyl substituted in the 2- or 3-position by C₁ -C₄ alkoxy, by di(C₁ -C₄ alkyl)amino or by a 1-pyrrolidyl, 1-piperidyl or 4-morpholinyl group; C₅ -C₈ cycloalkyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl; benzyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl; tetrahydrofurfuryl or a group of the formula (III), or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR28## with R being a group of the formula (III).
 4. A compound of the formula (I) according to claim 1, in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) in which R₂ is hydrogen, C₁ -C₁₀ alkyl, C₂ -C₃ alkyl substituted in the 2- or 3-position by methoxy, by ethoxy, by dimethylamino, by diethylamino or by 4-morpholinyl; cyclohexyl which is unsubstituted or mono-, di- or tri-substituted by C₁ -C₄ alkyl; benzyl, tetrahydrofurfuryl or a group of the formula (III), or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR29## with R being a group of the formula (III).
 5. A compound of the formula (I) according to claim 1, in which X and Y which can be identical or different are a group of the formula (IIa) or (IIb) in which R₂ is hydrogen, C₁ -C₈ alkyl, cyclohexyl, benzyl or a group of the formula (III), or the two radicals X, the two radicals Y or the radicals X and Y, each, form together a group ##STR30## with R being a group of the formula (III).
 6. A compound of the formula (I) according to claim 1, in which X and Y are a group of the formula (IIa) or (IIb) in which R₁ is hydrogen or methyl, R₂ is hydrogen or C₁ -C₄ alkyl, or the two radicals X and the two radicals Y, each, form together a group ##STR31## with R being a group of the formula (III).
 7. A compound according to claim 1, of the formula ##STR32## 